Soil cone penetrometer resistance is a good measure of soil strength in relation to root growth, carrying capacity and trafficability. The cone penetrometer can be used as an indicator of the effect of agricultural management practices on soil quality provided the equipment has the capacity to provide detailed and accurate data. Currently, the collection of penetration resistance data requires either the use of heavy mounted equipment or the use of lightweight equipment which requires that the operator manually provide the required force to push the penetrometer into the soil. The accuracy of the data is comprised by the operator's inability to apply a constant force and rate of loading during the penetration.
Assessment of the spacial variability of the penetration resistance requires the equipment to be portable over a wide range of field and crop conditions. The penetration resistance values of soil vary with water content and there is a need to collect water content values to improve the interpretation of the data.
The successful operation of known arrangements relies on the operator controlling and maintaining a constant rate of penetration and applied force during insertion of the penetrometer probe. This is substantially difficult, if not impossible, in soils having layers of varying strength and/or resistance. In addition, the representativeness of the penetrometer measurements is dependent on operator strength and mass which influences one's ability to control both the rate and force parameters. The measurement of soil water content, which is critical for the interpretation of penetration resistance, requires either the instrumentation of an adjacent site for in-situ measurements or the collection of soil samples from each depth increment for laboratory determination of water content. Additional variability is introduced into the data set by this requirement to sample the two neighbouring sites; this serves to compound the statistical analysis by creating added variability within the data set.
In terms of the arrangements which have been proposed in the prior art, U.S. Pat. No. 5,316,950, issued May 31, 1994, to Apitz et al is an example. This reference is reference to a method for quantitative calibration of in-situ optical chemical measurements in soils using soil class and characteristics wherein the probe which optically collects data regarding chemical constituents present within the soil and compares this to known values. This apparatus does not appear to be portable and further, does not make any reference to the use of a constant force apparatus for delivering the probe into the soil or substrate sample to be tested.
Grey et al., in U.S. Pat. No. 5,246,862, issued Sep. 21, 1993 provide a method and apparatus for in-situ detection and determination of soil contaminants wherein the penetrometer provides a reagent carrying tape between the soil and the outer wall of the penetrometer. As the penetrometer is injected into the soil, the tape is pressed against an optical window in the penetrometer and contaminants in the soil react with the reagents and cause a chemical reaction of the tape to occur which is optically detected by the probe.
Similar to U.S. Pat. No. 5,316,950, this reference does not provide for a penetrometer which is capable of controlled and constant force application for the delivery of the probe into the soil and further, the probe does not include means for detecting soil moisture within a substrate sample.
U.S. Pat. No. 4,061,021, issued to Baldwin et al., Dec. 6, 1977, provides a recording soil penetrometer. The penetrometer provides a recording drum which is rotatably mounted to the frame of the apparatus for recording pressure sensitive data thereon. Although the data with respect to the force applied is useful, the apparatus provided for in this reference does not provide a delivery system for the probe which is capable of delivering the probe at a constant force while at the same time providing means for determining the soil moisture content of the soil being tested.
A self-recording portable soil penetrometer is provided in U.S. Pat. No. 3,712,121, issued to Fletcher et al., Jan. 23, 1973. The penetrometer provides the recording drum which is rotatable according to the force applied on the handle of the apparatus and additionally provides a stylus for marking the drum along its height according to the penetration depth of the probe in the soil.
Additional patents which relate to the penetrometer include, for example, U.S. Pat. Nos. 5,313,825, issued to Webster et al. May 24, 1994, U.S. Pat. No. 3,331,240 issued Jul. 18, 1967 to Nilsson et al., U.S. Pat. No. 3,481,118 issued Dec. 2, 1969 to Mori, U.S. Pat. No. 3,999,424 issued Dec. 28, 1976 to Saint-Remy Pellissier, U.S. Pat. No. 5,067,346, issued Nov. 26, 1991 to Field, and U.S. Pat. No. 5,010,776 issued Apr. 30, 1991 to Lucero et al.
In view of what the prior art has previously proposed, it is clear that there exists a significant need for a penetrometer which incorporates numerous features in order to provide a host of data necessary for proper soil analysis. In addition, the need for a penetrometer which eliminates various parameters as variables is required in order to simplify collected data in order to provide an accurate soil representativeness determination. The present invention is directed to satiating these needs.